Christmas Tree Worms thrive on ocean coral reefs worldwide but there’s one day each year when they can really strut their stuff… can you guess which one?

Known to marine biologists as Spirobranchus giganteus, Christmas Tree Worms are a species of tube-building polychaete worms belonging to the Serpulidae family. Now forget everything you think you know about worms – far from the pallid, slimy and supremely unassuming critters most often seen after it rains or on the end of a fishhook, Christmas Tree Worms are true visual wonders!

They’re called Christmas Tree Worms because, well, just look at ’em! To be fair, the “Christmas Trees” are only one part of the creature, undoubtedly the rest of their bodies look like the bristly segmented worms they are.

Most divers and photographers (and especially, diving photographers) only see the worm’s dazzlingly beautiful, often multicolored, double-spiraled fans that do double duty as feeding appendages and gills. There’s more to them than meets the eye, however.